Five members of the Welsh Language Society have ended a day-long occupation of Mynyddcerrig junior school in the Gwendraeth valley.
The council said the school building has been offered to the community
The group broke into the school near Kidwelly, in protest at its closure and changed the locks.
They say the building could become a focal point for the community but the council want to sell it - something the council denied.
Councillor Ieuan Jones described it as a "criminal act for publicity".
The five forced their way into the former Welsh-medium primary, which had seen previous protests by parents and the local community over its closure.
The school - which had 16 pupils - shut in July as part of reorganisation.
Carmarthenshire has a 10-year schools' reorganisation programme, aimed at improving school buildings as well as cutting surplus places, that could see up to 32 schools closed and replaced with new area "super schools".
Carmarthenshire Councillor Ieuan Jones, the executive board member for education, described the protest as "a nonsense".
He said: "I can't understand why they're there. We're offering the school to the community if the community wishes to take on the challenge. It's part of our policy.
"The consultation process took a period of over nine months and, as a matter of fact, when the school was already unable to fund itself, we actually put in more money into that school in order to keep the teacher there until the school actually closed.
"So we've bent over backwards in the case of Mynyddycerrig."
After the protest, campaigner Ffred Ffransis accused the council of "going through the motions" in offering the school building to the community.
"It's if they can get a business plan together almost immediately and if there are exceptional circumstances - it's not going to happen," he said.
"They're going to try to sell off the building as quickly as possible and raise money for the council, it doesn't matter about the local community, the parents or the children's education."